ISS013-E-74843 (2 Sept. 2006) --- Rio Negro in Amazonia, Brazil is featured in this image photographed by an Expedition 13 crewmember onboard the International Space Station. The wide, multi-island zone in the Rio Negro (Black River) shown in this image is one of two, long "archipelagoes" upstream of the city of Manaus (not shown) in central Amazonia. Ninety kilometers of the total 120 kilometers length of this archipelago appear in this view. On the day the photo was taken, air temperatures over the cooler river water of the archipelago were just low enough to prevent cloud formation. Over the neighboring rainforest, temperatures were warm enough to produce small convection-related clouds, known to pilots as "popcorn" cumulus. Several zones of deforestation, represented by lighter green zones along the river banks, are also visible. Two different types of river appear in this image. Flowing east-southeast (left to right) is the multi-island, Rio Negro, 20 kilometers wide near the right of the view. Two other "black" rivers, Rio Caures and Rio Jufari, join Rio Negro downstream. The second river type is the Rio Branco (White River; right) which is the largest tributary of the Rio Negro. The difference in water color is controlled by the source regions: black-water rivers derive entirely from soils of lowland forests. Water in these rivers has the color of weak tea, which appears black in images from space. By contrast, white-water rivers like the Branco carry a load of sand and mud particles, mudding the waters. The reason for the tan color is that white-water rivers rise in mountainous country where headwater streams erode exposed rock. The Amazon itself rises in the Andes Mts., where very high erosion occurs, and it is thus the most famous white river in Amazonia. This image was taken in September, near low-water stage. Pictures taken at other times show the channels much wider during high-water season (May--July) when water levels rise several meters. It was discovered recently, from high resolution GPS measurements at Manaus, that the land surface actually rises vertically a small amount in compensation when this vast mass of water drains away each season. Although small, the vertical displacement--50-70 mm--was unexpectedly large according to the scientists who performed the study.